A toroidal type continuously variable transmission is a continuously variable transmission with which the speed change ratio between the power input shaft and the power output shaft can be continuously varied, and a structure therefor is disclosed, for example, in Tokkai Hei 7-243499 published by the Japanese Patent Office in 1995.
In this transmission, a power input disk and a power output disk are supported by radial bearings on the outer surface of the power input shaft, and a plurality of power rollers are arranged in a toroidally shaped space which is defined between these two disks. The power output disk is fitted loose on the power input shaft so as to be free to rotate relative to the power input shaft, but its axial displacement is limited by a bearing. The power input disk is also fitted loose on the power input shaft, but when the power input shaft rotates, cam rollers exerts axial pressure on the power input shaft towards the power output shaft, by which the power rollers are squeezed between the power input and output disks, and due to this axial pressure the input disk rotates together with the power input shaft.
The power rollers are rotated by the rotation of the power input disk and their rotation is transmitted to the power output disk. The power rollers can be inclined via trunnions to any desired angle in the interior of the toroidal space, and, according to this angle of inclination, the rotational speed ratio between the power output disk and the power input disk can be altered as desired by change of the contact positions of the power rollers with these disks.
In this transmission, various members such as the power input disk, the power output disk, the cam rollers and so on are housed within a casing while in a state of being loaded upon the outer surface of the power input shaft. Further, conventionally, the tip of the power input shaft is supported via a radial bearing in a tubular shaped support portion which is formed in the casing.
Since it is necessary to load the various parts onto the power input shaft, it is necessary for the diameter of this power input shaft to be reduced in steps towards its tip, and thus its tip, which is supported in the aforesaid radial bearing, has the smallest diameter of any portion thereof.
For this reason, in this transmission, in order to ensure adequate support force for the tip portion of the power input shaft in the radial direction, it is necessary to make the length in the axial direction of this bearing large, and it is inevitable that this will cause increase in the size of the transmission.
Further, since the support strength of this relatively small diameter tubular shaped support portion tends to be low, it can easily be deformed by loads which act upon the power input shaft. However, if this tubular shaped support portion is even a little deformed, the power input shaft may become tilted with respect to the power input disk or to the power output disk, and this is a primary factor leading to the generation of vibration and noise.
Since the power input shaft supplies lubricating oil to the cam rollers which generate a high thrust force, it is formed to be hollow. However, even if this hollow portion has an opening at the tip of the power input shaft, since the tip portion of the power input shaft is inserted into the inside of the tubular shaped support portion, the opening is undesirably blocked by the tubular shaped support portion, and it is difficult to provide an oil conduit from this opening to arrive at the cam faces of the cam rollers.
For this reason, the structure of the supply conduit for the lubricating oil to the cam rollers inevitably becomes complicated.